Scanning probe microscopy (SPM) is a microscopy technology which is able to form images of specific targets using different sensing modalities. SPM is based on the controlling of the interaction between the sample surface and the probe and the scanning of the probe on or near the sample surface. To form images, SPM raster scans the probe over the sample surface, the surface information, such as height, or phase, etc., can be recorded and reconstructed by a computer. The type of the surface information depends on the different types of interaction between the probe and the sample surface.
There are a plurality of established types of SPMs, such as scanning capacitance microscopy (SCM), scanning tunneling microscopy (STM), magnetic force microscopy (MFM), and atomic force microscopy (AFM), etc. The interaction between the probe and the sample surface can be categorized as a contact mode, a non-contact mode, or an intermittent mode (or taping mode), etc.
Amongst of the SPMs, SCM is able to obtain a two-dimensional doping profile of the to-be-test device structure with a spatial resolution in a range of approximately 10 nm˜15 nm and a doping concentration in a range of approximately 1E15 atoms/cm3˜1E20 atoms/cm3. SCM is a contact mode SPM, during the imaging process, the probe needs to contact with the sample surface; and mechanically scan on the sample surface; and thus it requires the sample surface to be significantly smooth to obtain the electrical signals.
However, the surface roughness of the to-be-tested device structure formed by an existing method is relatively large; it is unable to match the requirements for performing the contact mode SCM testing. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems